Nursery Nutrient Loading Increased Growth and Nitrogen Retranslocation in Jack Pine (Pinus banksiana Lamb.) Seedlings Planted on an Oil Sands Reclaimed Soil.

Growth of planted seedlings can be reduced by low nutrient availability and high understory vegetation competition in reclamation of disturbed landscapes. Nutrient loading of seedlings in nursery by exponential fertilization has shown to improve seedling growth in highly competitive and nutrient poor sites. We evaluated the impact of exponential fertilization in nursery and weed removal in the field on growth and nitrogen (N) retranslocation and uptake from the soil of jack pine (Pinus banksiana Lamb.) seedlings planted on reconstructed soils in the oil sands region in northern Alberta. The N retranslocation was traced using 15N isotope labeling. Exponential fertilization increased nutrient reserve in the seedling as compared to conventional fertilization in nursery production. Exponential fertilization increased height (p = 0.003), root collar diameter (p < 0.001), total biomass (p < 0.001) and N content (p < 0.001) of seedlings at the end of first growing season. Conventionally fertilized seedlings allocated a greater percent of biomass to roots than to current-year needles. The 15N isotope analysis showed that 59 to 82% of total N demand of new growth was met by retanslocation from old tissues. Exponential fertilization increased N retranslocation by 147% (p < 0.001) and N uptake from the soil by 175% (p = 0.012). Weed removal marginally increased (p = 0.077) N uptake from the soil but decreased (p = 0.046) N retranslocation in exponentially fertilized seedlings with no net effect on total N content in new tissues. We conclude that exponential fertilization improved the early growth of jack pine and can help improve revegetation in reclaiming disturbed oil sands sites.